For many years, strong river and tidal currents have posed problems in navigation, ship handling and shoreline erosion. The navigation problem in rivers stems from the fact that the currents cause bed erosion up-river and accretion down-river. The current, then, causes the accreted beds to meander. This is particularly true on the Mississippi River system, where bars appear at bends and, then, disappear. The U. S. Coast Guard has been responsible for marking these meandering bars. In order to warn mariners of the presence of sand bars, fast-water buoys have been deployed by the Coast Guard. These fast-water buoys have two major problems. The first is that the buoy motions become unstable at certain current speeds, as described by McCormick and Folsom (1973) and others. The second problem is that the buoys are subject to mooring failures caused by fatigue or collisions with passing vessels. These problems could be alleviated by more permanence in the bar locations.
Many vortex-induced-motions (VIM), vortex-induced vibration (VIV) and wake-force studies have been performed since the middle of the last century. Normally, VIM studies involve moored bluff bodies; while, VIV studies are devoted to cables. The characterization of these studies and sample studies are as follows:                (a) Vortex-induced forces on fixed, rigid bodies, as by Sobey and Mitchell (1977).        (b) 2-Dimensional vortex-induced transverse motions, as by Bernitsas et al (2006), Farshidianfar and Zanganeh (2009), Leong and Wei (2008), Ng et al (2001) and Ogink, and Metrikine (2010).        (c) 2-Dimensional vortex-induced (un-coupled or coupled) in-line and transverse motions, as by Cebron et al (2008), Jauvitis, and Williamson (2004), Ryan (2002) and Shiguemoto et al (2010).        (d) 3-Dimensional vortex-induced motions, as by Rodenbusch, G. (1978).        
These can further be sub-classified as current-induced and wave-induced. The analyses can be linear-harmonic or non-linear wake-oscillator. The latter involves the use of the van der Pol equation to represent the lift force produced by the wake hydrodynamics. An excellent compilation and discussion of all of the pre-1990's results can be found in the book by Blevins (1990).
The analysis is partially empirical in nature due to the coefficients based on the experimental reports of McCormick and Steinmetz (2011) and McCormick and Murtha (2012). The experiments referred to were conducted using a bi-modal buoy equipped with vertical fins and a horizontal damping plate. That buoy system is designed to absorb and dissipate wave energy. The experiments were conducted in a 117-meter wave and towing tank. The analysis of the interaction of the fin-spar buoy (FSB) and a current is guided by the analysis of Rodenbusch (1978), and the performance as an energy dissipater follows the energy analysis that leads to a hydraulic jump.
U.S. Patent Publication No. 2011/0299927 (McCormick, et al.), which is owned by the same Assignee, namely, Murtech, Inc. of Glen Burnie, Md., as the present application, is directed to a buoy for use in reducing the amplitude of waves in water and a system making use of plural buoys to create a floating breakwater.
However, there presently exists a need for a buoy that absorbs and attenuates the energies of streams and rivers which overcomes the disadvantages of the prior art. The subject invention addresses that need.